Recently, plastic materials have been used for optical parts in place of inorganic glass, especially for eyeglass lenses, because they are lightweight and have good dyeability and good impact resistance. In particular, a diethylene glycol bisallylcarbonate polymer (hereinafter referred to as CR-39) has been used, primarily for plastic lenses. However, it has a refractive index of 1.50, which is lower than that of inorganic glass. Although lenses made of CR-39 have relatively strong power, they are thick and do not generally have a good appearance. Various types of high-refractive-index, low-chromatic-aberration plastic lenses have also been tried, but they are also not free from problems.
Ordinary plastic lenses are poor in scratch resistance. It has been known to provide a silicone-based, hard coat layer on the substrate surface of plastic lenses to improve scratch resistance. In addition, the hard coat layer can be overcoated with an inorganic antireflection layer. The reflection layer can be applied, for example, by vacuum vapor deposition. The added antireflection layer provides the additional benefit of reducing surface reflection that could cause image flickering. In addition, an outer layer can be provided to protect the inner layers from aging. A problem that occurs, however, in forming both a hard coat layer and an antireflection layer on the surface of a plastic substrate is that the impact resistance of the lenses is low.
One means for improving the impact resistance of lenses comprising a low-refractive-index substrate, such as CR-39, is to form a thermosetting or thermoplastic resin layer between the substrate and the hard coat layer (JP-A-63-87223, JP-A-63-141001). However, lenses which have a high-refractive-index substrate, such as polythiourethane, and a resin layer, will exhibit interfacial light interference due to the difference in refractive index between the substrate and the hard coat layer. The result will be diminished optical quality, as well as inferior appearance. For lenses of that type, a technique of forming a primer layer of a thermosetting or thermoplastic resin that contains particles of dispersed metal oxide has been used (JP-A-9-80206, JP-A-9-291227). However, this method of incorporating particles of metal oxide in the primer layer is problematic in that the impact resistance of the lenses is lowered, even though the refractive index of the layer can be increased.